x402-一种互联网原生支付的开放标准 An open standard for internet-native payments

x402:Anopenstandardforinternet-nativepayments

An

HTTPbasedprotocolforagents

,contextretrieval,APIs,andmore

By:

ErikReppelRonnieCaspersKevinLeffewDannyOrgan

DanKimNemilDalal

CoinbaseDeveloperPlatform

/x402

May6,2025

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Contents

1Motivation

3

2OnchainPayments:TheFoundationofAutonomousDigitalEconomies

3

2.1WhereTraditionalPaymentRailsFail

3

2.2ScalingPaymentswithBlockchainandDigitalAssets

4

3Howx402Works

4

3.1ExampleIntegration

5

3.2CorePaymentFlow

5

4x402EnablesFrictionlessPayments

5

5CreatingaPaymentLayerforAgenticCommerce

7

5.1EmpoweringAgentstoTransactAutonomously

7

6EnablingNewBusinessModels

8

6.1PragmaticMicropayments

8

6.2SeamlessPay-Per-UseMonetization

8

7SimplifyingPaymentsOperations

8

7.1MitigatingFraud,Chargebacks,andComplianceOverhead

8

7.2Future-Proof,Chain-andToken-AgnosticPayments

9

8Thex402Spec:AFlexibleHTTPStandardforPayments

9

8.1MiddlewareConfiguration

9

8.2HandlingRequestsWithoutPayment

9

9TechnicalSpecifications

10

9.1PaymentRequestFormat

10

9.2PaymentAuthorization

10

9.3TransactionSettlement

10

10IntegrationExamples

11

10.1Server-SideImplementation

11

10.2Client-SideImplementation

11

10.3WalletIntegration

12

10.4TestingandDevelopment

12

11UseCases:RealWorldApplicationsofx402

13

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12KeyTakeaways

13

13ReferenceImplementation

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Abstract

x402isanopenpaymentstandardthatenablesAIagentsandwebservicestoautonomouslypayforAPIaccess,data,anddigitalservices.Byleveragingthelong-reserved

HTTP402

”PaymentRequired”statuscode,x402eliminatestheneedforAPIkeys,subscriptions,andmanualpaymentprocessing,allowingreal-time,machine-nativetransactionsusingstablecoinslikeUSDC.

Withonelineofcode,developerscanintegratepay-per-usemonetization,unlockingfrictionlesspaymentsforcontextretrievalandthird-partyAPIsforAI-drivenapplications.x402offersinstantsettlement,near-zerofees,andchain-agnosticflexibility,makingittheidealsolutionforAI-firstcommerceandmachine-to-machinepayments.

Motivation

TherapidgrowthofAIandautonomoussystemsisreshapingtheinterneteconomy,butoneofthemajorroadblockstoachievingfullyautonomousAIsystemsisthelackofapaymentsystemthatempowersAIAgentstofunctionwithouthumanintervention.

Legacypaymentsystemsaredesignedprimarilyforhumaninteractions.Assuch,webservicesare:notabletobeusedautonomouslybyAIagents,stuckusinginefficientbusinessmodelslikesubscriptions,andhinderedbyoperationalcomplexitiessuchasdelayedsettlementtimes,hightransactionfees,manualinvoicing,andsusceptibilitytofraudandchargebacks.

ThesechallengescreatesignificantfrictionforAI-drivenapplicationsandmachine-to-machine(M2M)transac-tions,preventingthefullrealizationofautonomousdigitaleconomies.AIagentsrequireinstant,frictionlessaccesstoreal-timecontextualdata,APIservices,anddistributedcomputingresourcestofunctionindepen-dently.Theyneedtheabilitytoexecutemicrotransactionsdynamicallyandautonomously,withoutthehuman-in-the-loopinterventionordelaysassociatedwithlegacypaymentsetups.

BrowserUsageAPIshaveattemptedtoaddresscertainrequirementsofagenticpayments,theycontinuetoleveragesystemsoriginallydesignedforhumanusersratherthanmachines.Consequently,theyremainburdenedbymanualuserexperience(UX)navigation,relianceoncreditcards,accountverificationprocesses,andtheoverallhuman-orientedfrictionthatimpedestrueautomationforagenticinteractions.

Ultimately,themotivationbehindx402istounlockthefullpotentialofautonomousAIsystemsandagenticcommerce,fosteringamoreefficient,frictionless,andscalabledigitaleconomyfortooluse.

Byenablingmachine-nativepayments,x402enablesAIagentstoautonomouslydiscoverandprocurethird-partycloudresources,contextualdata,andAPItools—makingiteasierforthemtoachievetheirtargetedoptimizationgoalswithouthuman-in-the-loopintervention.Thisempowersdevelopers,businesses,andconsumerstoinnovatefreelywithoutpaymentfriction,acceleratingtheadoptionandevolutionofAI-drivencommerce.

OnchainPayments:TheFoundationofAutonomousDigitalEconomies

WhereTraditionalPaymentRailsFail

Legacypaymentsystemsincurhighcosts,slowsettlementtimes,chargebackrisks,andrequirelayersofmanualsetupandauthorizationmakingthemimpracticalforAI-drivencommerce.

Forexample,ACHbanktransferstake1—3daystosettle,whileevencreditcardpayments—despiteinstantauthorization—cantakedaystofinalizeandremainsubjecttoreversalformonths.Additionally,traditional

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systemspresentsignificantbarrierstofinancialinclusion,leavingapproximately1.4billionpeopleunbankedandwithoutaccess(

source

).

x402bridgesthegap,allowingAIagentsandAPIproviderstointeractseamlesslywithreal-time,trustlesspayments—eliminatingfrictionfromlegacybillingsystemsandunlockingnewpay-per-userevenuemodels.

ScalingPaymentswithBlockchainandDigitalAssets

Comparedtolegacypaymentrails,onchaintransactionsviax402settlein~200ms,providinginstantpaymentfinalityforAPIproviders.Norollingchargebackwindows,nosettlementdelays—justreal-timeaccessandrevenuecollection.Builtonpermissionlessblockchaininfrastructure,x402isavailableworldwidewithoutrequiringcostlyconversionsoraccesstotraditionalfinancialrails.Forabroaderdiscussiononhowonchainpaymentsaretransformingdigitalcommerce

(B,2025)

.

x402eliminatestheseinefficienciesbyleveragingstablecoinsandLayer-2scalingforlow-cost,instant,andautomatedtransactions.Thetablebelowcomparesx402withtraditionalpaymentmethods,demonstratingwhyitisoptimalforAI-first,pay-per-usemodels.

PaymentRail

TypicalFees

SettlementFinality

ChargebackRisk

Scalability

CreditCard

$0.30+2.9%

Days(batch)

Yes,upto120d

65kTPS*

*theoreticalmax

PayPal

~3%+markup

Instant

authorization,

settlementindays

Yes

Unknown

Stripe(PaywithCrypto)

1.5%+

Dependson

blockchain

No-notreversible

Dependson

blockchain

EthereumL1

$1—$5+gas

1—2minforconfirmations

No-notreversible

15—20TPS

x402(onBase)

Free*

*nominalgasi$0.0001

200ms

No-notreversible

Hundredsto

thousandsTPS

Howx402Works

x402isanopenpaymentsprotocoldevelopedbyCoinbasethatenablesAIagentstocompletetransactionsautonomously.Itispoweredbyonchaintechnologyanddigitalcurrencies(primarilystablecoinslikeUSDC)andprovidesalightweight,secure,andinstantaneouspaymentsystemthatwehopecanhelpacceleratetheadoptionofM2Mpaymentsandagenticcommerce.

Thex402protocolutilizesthelong-reserved

HTTP402

”PaymentRequired”statuscodetorequireapaymenttocompleteanAPIrequestorloadawebpage.IfanAPIrequestlackspayment,x402respondswithan

HTTP402PaymentRequiredstatus

,promptingtheclienttopayandretry.

Withthissimpleprotocol,x402removestheneedforAPIkeys,accounts,andsubscriptions.x402enablesanyAPIorcontentprovidertoacceptpay-per-usepaymentsthroughalightweightmiddlewarethatintegratesseamlesslyintoexistinginfrastructures.

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ExampleIntegration

Withonelineofcode,companiescanmonetizeAPIs,content,andservices:

paymentMiddleware(amount:"0.10",address:"0x...")

CorePaymentFlow

1.ClientRequest—AIagentorapprequestsaccesstoanAPIordigitalresource.

2.PaymentRequired(402)—Ifnovalidpaymentisattached,theserverrespondswith

HTTP402

,providingpricingandpaymentdetails.

3.AgentRetriesRequestwithSignedPayment—Theagentsubmitsasignedpaymentauthorizationaspartoftheretriedrequest.

4.WebServiceVerifies&BroadcastsPayment—Theservervalidatesthepayment,broadcastsit,andreturnsaresponsetotheAPIrequest.

Figure1:x402PaymentFlow:AIAgent艹APIServer艹Blockchain

x402EnablesFrictionlessPayments

x402removesaccountandbillingfrictionfrompayments,enablingtruepay-per-useaccesswithoutsubscrip-tions,prepaidcredits,ormanualinvoicing.Here’showbothAIagentsandhumanscanusex402toaccessdigitalservicesinstantly:

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Figure2:Comparison:ExistingAgentPaymentProcessvs.x402Pay-Per-UseSimplicity

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Scenario

TraditionalProcess

Withx402

AIAgents:

AutonomousResearch

Assistant

•Requiresmultipleaccountsubscriptionsforinferenceanddataaccess.

•Designedforhumanstomanually

createanaccount&setupAPIkeys.

•APIwhitelistingorapprovalmayberequiredbeforeuse.

1.AIagentrequestsmarketdataAPI

2.APIrespondswith

HTTP402

PaymentRequiredandcostdetails

3

.AIagentattachesUSDCpaymentandretries

4.InstantAPIaccessgranted,immediatecontextretrieval

HumanUsers:Pay-Per-ArticleNewsAccess

•Requiresaccountsignup&paymentdetails.

•Forcessubscriptionmodel,eveniftheuseronlywantsonearticle.

•Usermustcancelmanuallytoavoidrecurringcharges.

1.Userclickspaywalledarticle

2.

HTTP402PaymentRequiredshows

USDCcost

3.Userconfirmspaymentincryptowallet

4.Articleinstantlyunlocked,nostoredcreditcards

AccessControl

Tofurtherenhancecontentsecurityandaccesscontrolafterpayment,x402canbecombinedwithdecentralizedauthorizationsolutions,enablingcontentproviderstoenforcegranularaccessrules(e.g.,single-useURLs,IP-restrictedcontentstreams)withoutcentralizedauthorizationservers.

CreatingaPaymentLayerforAgenticCommerce

Today’slegacypaymentsystemswerebuiltforhumans—requiringcreditcards,subscriptions,andman-ualinvoicing—makingthemincompatiblewithautonomousAIagents,APIs,andmachine-to-machinetransactions.

AsAIsystemstakeonmoreautomated,decision-makingroles,theyneedapaymentinfrastructurethatisseamlessandfrictionless,enablingautonomousagentstorapidlyaccesscontext,retrievereal-timedata,andexecuteactionsonthird-partysystemswithoutdelayorhumanintervention.

EmpoweringAgentstoTransactAutonomously

AImodelscannowoperateautonomously—butpaymentsremainabottleneck.Withoutamachine-nativesolution,languagemodelsstilllargelydependonhumaninterventiontoaccesscontextandactionsexternaltotheagentmodel.

x402eliminatesthisneedforhumanintervention,providingacrypto-nativepaymentstandardthatallowsAIsystemsto:

•PayperAPIrequest,dataquery,orAImodelinferencewithoutpre-registeringanaccount.

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•Fetchreal-timeinformationdynamically(e.g.,financialmarketdata,cloudresources).

•Seamlesslyinteractwithonchainandoffchainservices,triggeringpaymentsautonomously.

Thisenablesfullyautonomous,AI-drivencommerce—allowinggoal-orientedagentstooperateindependentlyinanon-demand,permissionlesseconomy.

EnablingNewBusinessModels

PragmaticMicropayments

Legacypaymentrailsoperateonanaccount-basedmodelandgenerallyrequiresomedegreeoftrust/creditriskamongcounterparties.

Theserailsweredesignedforhumans,anddon’tworkforsmall,high-frequencytransactionalserviceslikeAPIrequests.Withfeesashighas$0.30pertransaction,microtransactionsbecomeimpractical—forcingbusinessestorelyonsubscriptionsandbundledpricing,causingmanypotentialconsumerstoabstainfromuse.

Asapaymentprotocol,x402makesitpossibletochargeperrequest,perservice,orpersecondofusagewith:

•Near-zerotransactioncoststhatenablepaymentsaslowas$0.001centsperrequest.

•Truepay-per-usepricingforAPIs,AIinference,andon-demandcontent.

•Machine-to-machinetransactionsthatallowIoTdevicesandAIagentstoautonomouslypayforresources.

Forthefirsttime,businessescanprofitablysupportmicropaymentsatscale,creatingnewmonetizationopportunitiesforAI-drivenplatforms.ThisismadepossiblebecauseoflowcostandhighspeedoftransactionsonrollupslikeBase,andtrustworthystablecoinslikeUSDCthatarepeggedtotheUSD.

SeamlessPay-Per-UseMonetization

Acceptingpaymentsonlinehastraditionallymeantforcingusersintoaccounts,managingAPIkeys,andhandlingmanualbillingcycles.x402removesthesebarriersbyoffering:

•Seamlessper-requestpayments—Nosubscriptions,noprepayments,nolock-in.

•Instant,finalizedtransactions—Nochargebacks,nofraudrisks,nointermediaries.

•AI-nativemonetization—LetAIagentsandhumanuserspaydynamicallywithoutpre-approvalsorAPIkeys.

Fordevelopersandbusinesses,thismeanshigherrevenue,lowercosts,andaseamlesspaymentexperience.

SimplifyingPaymentsOperations

MitigatingFraud,Chargebacks,andComplianceOverhead

Beyondtransactionfees,legacypaymentsystemsexposebusinessestorisksofchargebacks,fraud,operationallosses,andcomplianceoverhead.Withx402:

•Paymentssettleinstantlyonchain,eliminatingchargebacksanddisputes.

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•NoPCIcompliancerequiredfordevelopers,unlessafacilitatorchoosestoacceptcardpaymentsdirectly

•Norelianceonbanksorthird-partyapprovals,ensuringglobal,permissionlessaccess.

Byremovingtheseroadblocks,x402allowsbusinessestofocusongrowth,notpaymentcomplexities.

Future-Proof,Chain-andToken-AgnosticPayments

x402isbuilttosupportanystablecoin,digitalasset,orblockchain—unlockingflexibilitybeyondtraditionalpaymentproviders.

•WhileUSDCisoneofthefirstsupportedassets,x402isdesignedtosupportstablecoins,digitalassets,andmultipleblockchainnetworks.

•Businessesanddeveloperscanchoosethebestcryptocurrencyfortheirusecase,ensuringmaximumflexibility.

Thisfuture-readydesignensuresthatx402willcontinueevolvingasAI-drivencommercescales.

Thex402Spec:AFlexible

HTTPStandardforPayments

Thex402middlewareisalightweightintegrationthatenablespay-per-requestAPIpayments.Thefollowingsectiondetailshowdeveloperscanconfigurex402andhowAIagentshandlepayment-requiredresponsesinrealtime.

MiddlewareConfiguration

paymentMiddleware(amount:"0.10",address:"0x...")

Parameter

Description

amount

Costperrequest(e.g.,”$0.10”)

address

Walletaddresswherepaymentsarereceived

HandlingRequestsWithoutPayment

Ifarequestissubmittedwithoutpayment,theserverrespondswith

HTTP402

(PaymentRequired).TheresponseprovidesstructuredfeedbackforAIagentsandhumans,including:

{

"maxAmountRequired":"0.10",

"resource":"/api/market-data",

"description":"Accesstoreal-timemarketdatarequirespayment.",

"payTo":"0xABCDEF1234567890ABCDEF1234567890ABCDEF12","asset":"0xA0b86991C6218b36c1d19D4a2e9Eb0cE3606EB48","network":"ethereum-mainnet"

}

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Field

Description

maxAmountRequired

Paymentamountrequiredforaccess(e.g.,$0.10)

resource

TherequestedAPIendpointorservice

description(optional)

Custommessagedescribingpaymentdetails

payTo

Developer’swalletaddress(receivingpayment)

asset

Contractaddressforthetransaction

network

Blockchainnetworkidentifier

TechnicalSpecifications

x402implementsastandardizedapproachto

HTTP402responseswithprecisespecificationsforpayment

requestsandverification.

PaymentRequestFormat

WhenanAPIreturnsa402response,itincludesastructuredJSONpayloadwiththefollowingfields:

Field

Description

maxAmountRequired

Maximumpaymentamountrequired(e.g.,”0.10”)

assetType

Tokenstandard(e.g.,”ERC20”)

assetAddress

Contractaddressofthepaymenttoken

paymentAddress

Recipient’swalletaddress

network

Blockchainnetworkidentifier(e.g.,”base-mainnet”)

expiresAt

Timestampafterwhichthispaymentrequestisnolongervalid

nonce

Uniqueidentifiertopreventreplayattacks

paymentId

Uniqueidentifierforthispaymentrequest

PaymentAuthorization

Whensubmittingpayment,clientsincludeacryptographicallysignedmessagecontaining:

•Allfieldsfromthepaymentrequest

•Theactualpaymentamount(mustbe≤maxAmountRequired)

•Timestampoftheauthorization

•Cryptographicsignaturefromthepayingwallet

ThesignaturefollowstheEIP-712standard,enablingclearandsecurepresentationinwalletinterfaceswhenusersauthorizetransactions.

TransactionSettlement

x402implementationscanhandlesettlementthroughvariousmethods:

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•On-chainsettlement:Directblockchaintransactions

•Layer-2settlement:UsingoptimisticorZKrollupsforlowerfees

•Paymentchannels:Forhigh-frequencymicropaymentsbetweentrustedparties

•Batchedsettlements:Combiningmultiplemicropaymentsintoasingletransaction

Thisflexibilityallowsdeveloperstochoosethemostefficientsettlementmechanismfortheirspecificusecaseandtransactionvolume.

IntegrationExamples

x402isdesignedforstraightforwardintegrationacrossvariousprogramminglanguagesandframeworks.

Server-SideImplementation

ForNodeJSapplicationsusingExpress:

//Installwith:npminstall@x402/express-middleware

constexpress=require(’express’);

const{x402PaymentRequired}=require(’@x402/express-middleware’);

constapp=express();

app.get(’/premium-data’,x402PaymentRequired({amount:"0.10",

address:"0x1234...",

assetAddress:"0x2345...",//USDCcontract

network:"base-mainnet"}),(req,res)=>{

//Thiscodeonlyrunsaftervalidpayment

res.json({premiumData:"Valuableinformation"});});

app.listen(3000);

Client-SideImplementation

Forwebapplicationsusingthex402clientlibrary:

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//Installwith:npminstall@x402/client

import{x402Client}from’@x402/client’;

import{connectWallet}from’your-wallet-connector’;

constclient=newx402Client();

constwallet=awaitconnectWallet();

//Configuretheclientwiththeuser’swalletclient.setWallet(wallet);

//MakeAPIrequestswithautomaticpaymenthandlingtry{

constdata=awaitclient.fetch(’

/premium-data

’);console.log(data);//Thepremiumdata

}catch(error){

console.error(’Paymentfailed:’,error);}

WalletIntegration

x402isdesignedtoworkwithanycryptocurrencywalletthatsupportsstandardsigningmethods.Whenapaymentisrequired,thewalletinterfacedisplaysaconfirmationscreenshowing:

•Therequestdomain(e.g.,)

•Therequestedpaymentamount

•Thepaymenttoken(e.g.,USDC)

•Thespecificresourcebeingaccessed

Thistransparencyensuresusersalwaysknowexactlywhatthey’repayingfor,maintainingtrustbetweenserviceprovidersandusers.

TestingandDevelopment

Thex402toolkitincludesalocaldevelopmentenvironmentwith:

•Testwalletspre-loadedwithtesttokens

•MockAPIserversimplementingthex402protocol

•Toolingforsimulatingvariouspaymentscenarios

•Detailedloggingfordebuggingpaymentflows

Thesetoolsallowdeveloperstobuildandtestx402integrationswithoutconnectingtoproductionblockchainsorspendingrealtokens.

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UseCases:RealWorldApplicationsofx402

Here’showAIagentsandhumansareusingx402invariouscontexts:

AgentsAccessingAPIsforOnDemandRequests

•Aresearchplatformenablespay-per-articleaccess,eliminatingbundledpaywallsandallowingAI-driventoolstopayonlyforrelevantcontent.

•Avideostreamingserviceleveragesx402tochargepersecondofcontentwatched,replacingtraditionalsubscription-basedmonetization.

•AtradingAIretrievesreal-timestockmarketdatafor$0.02perrequest,payingonlywhenneeded.

Pay-Per-UseAIModelInferenceMonetization

•AcomputervisionAPIcharges$0.005perimageclassificationinsteadofafixedenterprisefee.

•AsyntheticvoiceAIcharges$0.10peraudioclip,enablingflexiblemonetization.

AgentsPayingforCloudCompute&Storage

•AnautonomousagentpurchasesGPUresourcesfor$0.50perGPU-minute,payingpercomputecycle.

•Agoal-drivenAImodelexpandscloudstorageasneededforcontextandreinforcementlearning,payingperGBstored.

ContextRetrievalforAgents

•AfinancialAIassistantpays$0.25perpremiumnewsarticleforresearch.

•Alegalresearchagentaccessescourtrulingsat$0.10perdocument,avoidingfulldatabasesubscrip-tions.

MicropaymentsforHumanAccesstoContent

•ASubstackwritercharges$0.25perarticleforcasualreaders,allowingpay-as-you-goaccessinsteadoffullsubscri